Cruise control and secondary brake switch

[Bob Disney]

2005 36' Monterey IV
We had a scan done while in Quartzite last winter trying to find why our cruise quit working
the results said that a secondary brake light switch was faulty
I  must be blind because I just cant seem to find it
Any help would be great, been without cruise fir the last 20,000 miles.
Really miss it
Thanks

Should have stated that all the brake lights work as required

[Steve Huber Co-Admin]

Bob,
The only other brake light switch in the CC circuit is the turn signal switch which should not impact the CC circuit. Look at the 2005 Patriot or 2006 Monterey wiring diagrams in Coach Assist for the brake light and CC circuits. The 05 Monterey diagrams are very hard to read but the 05 Pat and 06 Monti are the same so will reflect the 05 Monti model year. It could be the  smart wheel clock spring that is causing the issue. There is a connector (C35 on the diagram) located in the steering column where you can access the CC on/off signal from the smart wheel to see if the clock spring is OK
Steve

[Eric Maclean]

Bob
Page #52 in the 2005 Monterey wiring diagrams shows the complete brake light circuit including the cruise control
page # 53 for the cruise control circuitry

According to the brake light wiring diagram there is only one service brake light switch.the brake status to the ECM for cruise control is done through a relay
First check to make sure the brake lights work this will verify that the brake light switch and the K25 relay are working.
This is where the wiring diagrams are somewhat misleading as they show a cruise interrupt relay K4 on the front run board diagram but do not show it in the wiring diagram .instead they show the K19 relay which appears to be for the Alison automatic trans in one diagram and ECM cruise in another
check the K4 and K 19 relay to check its operation  as both relays should work together if they are wired
In the diagrams they show a diode for the brake light signal coming to the K 19 relay in one diagram they show it reversed in the circuit either way if that diode os blown the circuit won't work ( there would be no brake interrupt) check that and the relays function.

I'd first look at the K 19 relay for continuity between the 30 and 87a  terminals if there is no continuity the relay is bad
If there is continuity then you will need to check that the brake status signal is present I believe this signal is a ground signal by looking at the diagram for the smart wheel vip controller it appears the Cat ECM is looking for a status signal to verify the brakes are off and when the brakes are applied the K 19 relay is operated opening the circuit removing the status signal from the ECM ( this signal appears to be a ground ) so you are looking for a ground on terminal 30 of the relay base and that should be present at the 87a terminal until the brakes are applied at which time the relay opens and the ground is removed.




Hope this helps
Eric

[David Ciotti]

On my 2002 Marquis if the engine brake switch is on the cruise control is disabled.  The engine brake switch will also light the brake lights when the throttle position engages the engine braking.

[Bob Disney]

On our coach the coach brake lights do not come on when the exhaust brake is activated, however the trailer and toad brakes are activated.
It has been this way since we have owned the coach
The exhaust brake worked with the cruise control on or off
Traveling on the interstate it is kind of handy to slow down gong down grades

[Bob Disney]

The clock spring is OK
I checked to see if the relays #18 and #19 were working and the both click when the brakes are applied
#18 is labeled as AUX brake
On relay #19 checked to see what wire go to which terminal according to what is written on each wire
#30 Service Brake
#95 Ground
#85- 2 brake light wires
#87 signal
Electric on vehicles is one of my many short comings, any help is very much appreciated

[Steve Huber Co-Admin]

Bill,
K19 wiring on pg 4 of 06 Monti wiring diagrams shows following:
 
  85: 2 wires, one  to pin 85 of K25 (Brake Lights) and one to CC cancel relay K4 (through a diode)
  86: Gnd
  87: Signal Rtn
  87A: no connection
  30: Svc brake status

so it's wired correctly. Suggest you check K4 to see if it is functioning. Easiest would be to replace it. All the other CC signals come from the smart wheel. K4 pin 85 should have no voltage on it unless the brake lights are on or there is a Cancel CC signal from the smart wheel.
Steve